The Human Endocrine System
& Homeostasis
Introduction:
● Different human mechanisms enable us to respond + react to outside environment to maintain
a constant internal environment
● Our responses = controlled by nervous + endocrine systems and to an extent, the immune
system
● These working together helps maintain stability in the organism and protects us
Nervous system responds to:
● A rapid respond to stimuli
● The use of electrical impulses + neurotransmitters
Endocrine response is controlled by the endocrine glands situated through the body
This response is:
● A slower response that has a long-lived effect
● As the endocrine gland produce + release specific hormones into the bloodstream
● An effector organ is targeted, and
● A response is inhibited
● When endocrine organs are either over or under stimulated, endocrine disorders are observed
Key Terminology:
Endocrine system ● System responsible for chemical coordination + regulation of various
activities in the body
Homeostasis ● Process of maintaining a constant internal environment (blood +
tissue fluid) in the body
Hormones ● Chemical messengers in body travels in the bloodstream + cause an
effect somewhere else in the body
Negative feedback ● Operate in human body to detect changes/imbalances in the internal
environment + to restore balance
Osmoregulation ● Regulation of water balance in the internal environment
Osmotic pressure ● A measure of concentration of solutes (eg. salt, glucose) present in
solution which may determine whether a cell loses/gains water
Antagonistically ● To work in opposite ways; if 1 hormone causes an increase of a
substance, the other hormone causes a decrease of that substance, eg.
insulin and glucagon
, Endothermic ● Relates to organism that generates heat internally through metabolic
process to maintain a constant body temp
Vasoconstriction ● Narrowing of blood vessels
Vasodilation ● Widening of blood vessels
Evaporation ● Heat loss when sweat changes into water vapour on surface of the
skin
Conduction ● Transfer of heat between objects = in contact
Convection ● As warm air rises it’s replaced by cooler air
Radiation ● Heat transfer between 2 objects that are not in contact
Thermoregulation ● Control of body temp to keep it as close to 37*C as possible
● Homeostasis = the tendency of an organism/cell to regulate its internal conditions, usually by
a system of feedback controls to stabilize health + functioning regardless of outside changing
conditions
Difference between the important Secretory Glands:
● Mammals produce secretion from exocrine + endocrine glands
Exocrine & Endocrine glands - Main Differences:
Exocrine glands Endocrine glands
● Have ducts ● Ductless
● Secretions released into cavity/on a ● Hormones released into bloodstream
surface ● examples : pituitary (ADH), thyroid
● Examples: salivary glands (saliva) + (TSH) + pancreas (insulin)
sweat glands (sweat)
● NOTE: the pancreas is both an endo- and exocrine gland
○ As an exocrine gland it secretes digestive enzymes into the small intestine
○ As an endocrine gland it secretes insulin + glycogen into bloodstream
, Endocrine glands:
● The endocrine system has endocrine glands that hormones into the bloodstream where they’re
transported to target site (like an organ)
● These hormones don’t work in isolation + often interact with other hormones in sequence of
events
● They work to produce a common effect or they work antagonistically
Hormones:
● They’re organic compounds that act as messengers in the body
● Most are proteins with some being steroids (lipids)
● They’re only needed in small amounts + give a more lasting response than a nerve response
● Hormones may be over-secreted/under-secreted, resulting in certain disorders
Basic Functions of Hormones:
● Reproduction, growth & development
● Maintenance of internal environment (by stimulating/inhibiting the functions of cells/organ)
● Regulation of metabolism by controlling production, usage + storage of energy
The Hypothalamus + Pituitary gland:
● Hypothalamus = small area of brain above, connected to pituitary gland + secreted important
hormones and is linked between the nervous + endocrine systems
● Hypothalamus plays an important role in controlling vital functions in the human body. We
will focus on ADH (antidiuretic hormone) produced by the hypothalamus
& Homeostasis
Introduction:
● Different human mechanisms enable us to respond + react to outside environment to maintain
a constant internal environment
● Our responses = controlled by nervous + endocrine systems and to an extent, the immune
system
● These working together helps maintain stability in the organism and protects us
Nervous system responds to:
● A rapid respond to stimuli
● The use of electrical impulses + neurotransmitters
Endocrine response is controlled by the endocrine glands situated through the body
This response is:
● A slower response that has a long-lived effect
● As the endocrine gland produce + release specific hormones into the bloodstream
● An effector organ is targeted, and
● A response is inhibited
● When endocrine organs are either over or under stimulated, endocrine disorders are observed
Key Terminology:
Endocrine system ● System responsible for chemical coordination + regulation of various
activities in the body
Homeostasis ● Process of maintaining a constant internal environment (blood +
tissue fluid) in the body
Hormones ● Chemical messengers in body travels in the bloodstream + cause an
effect somewhere else in the body
Negative feedback ● Operate in human body to detect changes/imbalances in the internal
environment + to restore balance
Osmoregulation ● Regulation of water balance in the internal environment
Osmotic pressure ● A measure of concentration of solutes (eg. salt, glucose) present in
solution which may determine whether a cell loses/gains water
Antagonistically ● To work in opposite ways; if 1 hormone causes an increase of a
substance, the other hormone causes a decrease of that substance, eg.
insulin and glucagon
, Endothermic ● Relates to organism that generates heat internally through metabolic
process to maintain a constant body temp
Vasoconstriction ● Narrowing of blood vessels
Vasodilation ● Widening of blood vessels
Evaporation ● Heat loss when sweat changes into water vapour on surface of the
skin
Conduction ● Transfer of heat between objects = in contact
Convection ● As warm air rises it’s replaced by cooler air
Radiation ● Heat transfer between 2 objects that are not in contact
Thermoregulation ● Control of body temp to keep it as close to 37*C as possible
● Homeostasis = the tendency of an organism/cell to regulate its internal conditions, usually by
a system of feedback controls to stabilize health + functioning regardless of outside changing
conditions
Difference between the important Secretory Glands:
● Mammals produce secretion from exocrine + endocrine glands
Exocrine & Endocrine glands - Main Differences:
Exocrine glands Endocrine glands
● Have ducts ● Ductless
● Secretions released into cavity/on a ● Hormones released into bloodstream
surface ● examples : pituitary (ADH), thyroid
● Examples: salivary glands (saliva) + (TSH) + pancreas (insulin)
sweat glands (sweat)
● NOTE: the pancreas is both an endo- and exocrine gland
○ As an exocrine gland it secretes digestive enzymes into the small intestine
○ As an endocrine gland it secretes insulin + glycogen into bloodstream
, Endocrine glands:
● The endocrine system has endocrine glands that hormones into the bloodstream where they’re
transported to target site (like an organ)
● These hormones don’t work in isolation + often interact with other hormones in sequence of
events
● They work to produce a common effect or they work antagonistically
Hormones:
● They’re organic compounds that act as messengers in the body
● Most are proteins with some being steroids (lipids)
● They’re only needed in small amounts + give a more lasting response than a nerve response
● Hormones may be over-secreted/under-secreted, resulting in certain disorders
Basic Functions of Hormones:
● Reproduction, growth & development
● Maintenance of internal environment (by stimulating/inhibiting the functions of cells/organ)
● Regulation of metabolism by controlling production, usage + storage of energy
The Hypothalamus + Pituitary gland:
● Hypothalamus = small area of brain above, connected to pituitary gland + secreted important
hormones and is linked between the nervous + endocrine systems
● Hypothalamus plays an important role in controlling vital functions in the human body. We
will focus on ADH (antidiuretic hormone) produced by the hypothalamus
